This invention relates to a load detection device for electromagnetically detecting load applied directly to a magnetic substance.
As a load sensor for measuring load applied to an elastic member, a strain gage type load cell has been known in which the strain of the elastic member deformed by a load is measured and the load applied to the elastic member is calculated from the strain measured.
However, the strain gage type load cell poses problems that its mechanical strength is low, the allowance for forces above the rated load is small because of its narrow dynamic range (range of load in use), measuring accuracy is not secured for a small load when it is of a high rating type, and it is complicated in its signal processor circuit because of week output signals and thus expensive.
In view of the foregoing, it is the object of this invention to provide a load detection device having a simple construction, a high mechanical strength and a wide dynamic range, capable of effecting smaller size, weight saving and cost reduction, and of achieving high response, as well as providing easy handling ability and easy adjustment, and suitable especially for transfer.
In order to achieve the foregoing object, this invention of claim 1 is characterized by a load detection device having a detection section including a coil and a solid rod-like magnetic substance disposed in the axial center of said coil, wherein said magnetic substance is magnetized by said coil, and load is applied directly to the magnetic substance to produce inductance change, so as to be detected.
The invention of claim 2 is characterized by the invention of claim 1, wherein a plurality of said detection sections are provided, said detection sections being adapted to produce a difference in inductance change for a load, and the load is detected from the difference in inductance change.
The invention of claim 3 is characterized by the invention of claim 2, wherein said difference in inductance change is produced by a difference in the magnetostrictive coefficient between magnetic substances used in said detection sections.
The invention of claim 4 is characterized by the invention of claim 2, wherein said difference in inductance change is produced by a difference in stress between magnetic substances used in said detection sections.
The invention of claim 5 is characterized by the invention of claim 2, wherein said difference in inductance change is produced by a difference in hardness of heat treatment between magnetic substances used in said detection sections.
The invention of claim 6 is characterized by the invention of claim 2, wherein said difference in inductance change is produced by a difference in magnetic permeability between magnetic substances used in said detection sections.
The invention of claim 7 is characterized by the invention of claim 1, wherein part of said magnetic substance is modified or deformed, and load is detected from a difference in inductance between the modified or deformed part and the other part of the magnetic substance.
The invention of claim 8 is characterized by the invention of claim 7, wherein means for partially modifying or deforming said magnetic substance is work hardening, heat treatment, surface treatment or diameter changing.
The invention of claim 9 is characterized by the invention of claim 2, wherein a plurality of detection sections are disposed coaxial with and opposite to each other, and a difference between output signals from detection sections is determined, so as to detect load applied to magnetic substances in the detection sections.
The invention of claim 10 is characterized by the invention of claim 2, wherein a plurality of detection sections are disposed coaxial and integral with each other, and load is applied at the central portion, so as to be detected in a plurality of directions.
The invention of claim 11 is characterized by the invention of claim 2, wherein a plurality of detection sections are disposed coaxial and integral with each other, a single magnetic substance common to the detection sections is provided, and the magnetic substance is fixed at the central portion, so as to detect load in a plurality of directions.
Therefore, according to this invention, the load detection device is composed of a solid rod-like magnetic substance and a coil for magnetizing the same, so that the diameter of the magnetic substance can be smaller and the construction is simplified, providing a device with a high mechanical strength and a wide dynamic range, capable of effecting smaller size, weight saving and cost reduction, as well as easy handling ability, and suitable for transfer.
Further, according to this invention, a magnetic substance with a small diameter is disposed at the axial center of a coil where the density of magnetic flux is the highest, so that energy necessary for magnetizing the magnetic substance can be kept minimum and inductance is kept small, thus providing easy high-frequency drive advantageous to detection.
Furthermore, according to this invention, load is applied directly to a magnetic substance and the load is detected from inductance change due to change in magnetic permeability of the magnetic substance caused by the load, so that no displacement is accompanied with detection, providing a structure capable of achieving high direct response and easy adjustment with small hysteresis, and unlikely to be affected magnetically.